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Growth optimization and applicability of thick on-axis SiC layers using sublimation epitaxy in vacuum
Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
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2016 (Engelska)Ingår i: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 448, s. 51-57Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

We demonstrate growth of thick SiC layers (100–200 µm) on nominally on-axis hexagonal substrates using sublimation epitaxy in vacuum (10−5 mbar) at temperatures varying from 1700 to 1975 °C with growth rates up to 270 µm/h and 70 µm/h for 6H- and 4H–SiC, respectively. The stability of hexagonal polytypes are related to process growth parameters and temperature profile which can be engineered using different thermal insulation materials and adjustment of the induction coil position with respect to the graphite crucible. We show that there exists a range of growth rates for which single-hexagonal polytype free of foreign polytype inclusions can be maintained. Further on, foreign polytypes like 3C–SiC can be stabilized by moving out of the process window. The applicability of on-axis growth is demonstrated by growing a 200 µm thick homoepitaxial 6H–SiC layer co-doped with nitrogen and boron in a range of 1018 cm−3 at a growth rate of about 270 µm/h. Such layers are of interest as a near UV to visible light converters in a monolithic white light emitting diode concept, where subsequent nitride-stack growth benefits from the on-axis orientation of the SiC layer.

Ort, förlag, år, upplaga, sidor
2016. Vol. 448, s. 51-57
Nyckelord [en]
Mass transfer;Substrates;Single crystal growth;Semiconducting materials
Nationell ämneskategori
Materialkemi
Identifikatorer
URN: urn:nbn:se:liu:diva-128610DOI: 10.1016/j.jcrysgro.2016.05.017OAI: oai:DiVA.org:liu-128610DiVA, id: diva2:930699
Tillgänglig från: 2016-05-25 Skapad: 2016-05-25 Senast uppdaterad: 2017-11-30
Ingår i avhandling
1. Sublimation Growth of 3C-SiC: From Thick Layers to Bulk Material
Öppna denna publikation i ny flik eller fönster >>Sublimation Growth of 3C-SiC: From Thick Layers to Bulk Material
2016 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

Silicon carbide (SiC) is a semiconductor material which holds high promises for various device applications. It can be obtained in different crystal structures called polytypes. The most common ones are hexagonal (6H- and 4H-SiC) and cubic (3C-SiC) silicon carbide. The 6H- and 4H-SiC single crystal substrates are commercially available, while technologies for the growth of 3C-SiC are still under development. The unique 3C-SiC properties like isotropy, narrower bandgap (2.4 eV)  compared to hexagonal polytypes (about 3 eV) and high electron mobility make it better over hexagonal counterparts for some semiconductor applications, for example, metal oxide semiconductor field effect transistors (MOSFETs). However, due to lack of high quality material, the full potential of 3C-SiC in device applications has not been revealed. In addition, it has properties suitable to explore new concepts in efficient photovoltaics or solar driven hydrogen generation by water splitting.

There is a need for 3C-SiC seeds to grow large 3C-SiC crystals by the widely used Physical Vapor Transport (PVT) technique. In case of hexagonal SiC polytypes such seeds were produced by the Lely method during which hexagonal SiC crystals spontaneously nucleate on the inner walls of a crucible. However, the formation of 3C-SiC using the Lely method is rarely observed. Therefore, the 3C-SiC has to be heteroepitaxially grown on silicon or hexagonal SiC substrates. Silicon is an inexpensive material with very high crystalline quality. However, due to almost 20% mismatch in lattice parameters and 8% difference in thermal expansion coefficient there is a high density of structural defects formed at the 3C-SiC/Si interface. In contrast, the 3C-SiC/hexagonal SiC material system does not encounter such problems, but there are other challenges like polytype stability or formation of structural defects called double positioning boundaries (DPBs).

This thesis work mainly focuses on the growth of 3C-SiC on hexagonal SiC substrates using sublimation epitaxy. The research covers the development of growth process for thick (~1 mm) 3C-SiC layers, advancement of the growth process to eliminate DPBs and growth of bulk material using thick 3C-SiC layers as seeds. The 3C-SiC was grown on off-oriented hexagonal SiC substrates. The surfaces of such substrates contain high density of steps. Therefore, they have mostly been used for the growth of homoepitaxial hexagonal layers or bulk crystals via step flow mechanism. However, as demonstrated in this thesis, under special conditions the 3C-SiC with high crystalline quality can also be grown on off-oriented hexagonal substrates. The stability window for the growth of hexagonal and cubic polytypes on nominally on-axis hexagonal SiC substrates is also explored. Moreover, it is demonstrated how the temperature profile inside the graphite crucible is influenced by the change in thermal insulation properties and how such change results in enhanced polytype stability during the growth of thick SiC layers. In addition, different sources for sublimation epitaxial growth of doped SiC layers were analyzed to gain further understanding of new parameter windows.

As a part of this thesis, a sublimation etching of 6H-, 4H- and 3C-SiC polytypes is presented using two different etching arrangements in vacuum (10-5 mbar) and Ar ambient. It is demonstrated that this technique can be used to remove residual scratches on the surface as well as to obtain various surface step structures which could be used for the growth of graphene nanostructures.

Ort, förlag, år, upplaga, sidor
Linköping: Linköping University Electronic Press, 2016. s. 45
Serie
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1760
Nationell ämneskategori
Fysik
Identifikatorer
urn:nbn:se:liu:diva-127802 (URN)978-91-7685-778-6 (ISBN)
Disputation
2016-06-09, Planck, Fysikhuset, Campus Valla, Linköping, 10:15 (Engelska)
Opponent
Handledare
Tillgänglig från: 2016-05-13 Skapad: 2016-05-13 Senast uppdaterad: 2016-11-23Bibliografiskt granskad

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